Molecular Regulatory Mechanism of Inflorescence, Flower and Fruit Development in Tomato

Tomato (Solanum lycopersicum L.) is a globally important vegetable crop and a key model species for studying reproductive development in other Solanaceae members with edible fleshy fruits, such as eggplant, sweet and hot peppers, and Physalis spp. The morphogenesis and patterning of tomato floral organs fundamentally determine fruit yield and quality. Recent advances in high-throughput sequencing and gene editing have significantly deepened our understanding of the molecular network regulating tomato reproductive development. This process, from the transition of vegetative shoot apical meristem to the inflorescence meristem, forming floral meristems with primordia of sepals, petals, stamens, carpels, and fruits, is precisely coordinated by a genetic network involving homeobox and other types of transcription factors, along with signaling pathways. This review systematically outlines the core regulatory network, with an emphasis on the MADS-domain transcription factor family and its associated ABCDE model. Integrating insights from hormone signaling and mutant phenotypes, we summarize the maintenance of inflorescence meristem identity, the specification of floral meristems, and the morphogenetic patterns and core gene regulatory mechanisms for each floral whorl in tomato. We further extend this framework to the flower-fruit continuum, examining how carpel development, floral meristem termination, and ovule differentiation influence fruit morphology, locule number, pericarp structure, and metabolic traits. Finally, we discuss the integration of floral organ development with molecular design breeding and formulate a forward-looking research agenda that translates floral regulatory mechanisms to breeding strategies for yield, uniformity, and fruit quality. This synthesis provides a theoretical foundation and genetic resources for the genetic improvement of tomato flower architecture and its underlying regulatory mechanisms.